Brian E Carpenter wrote:
No more than having your TCP use selective acks constitutes a 'dual
stack', relative to having TCP not use selective acks. While what I
suggested isn't that "minor" an enhancement to the stack, neither does it
constitute an entirely separate stack.
To repeat: Dual stack is entirely separate.
Not viewed from the socket programmer's point of view. Look at how an
AF_INET6 socket behaves when given an address like ::FFFF:192.0.2.3 afaik
the behavior is then exactly what you describe.
Apparently you missed most of the rest of my note, such as:
Yes, it is not perfectly compatible. The only way to achieve that is to
have purely syntactic differences.
Oh. Wait a minute. hat I described -- as a first step for adoption --
would have been a purely syntactic difference, albeit one that set the
basis for fixing the only problem that IPv6 was originally asked to
solve: bigger address space.
Exploiting that basis would have been moved to a strictly administrative
step. Prior to exploiting it, interoperability between IPv4 and IPv6
could have been perfect and easy.
The underlying point of my note was:
One would think that a 15-year project that was pursued to solve a
fundamental Internet limitation but has achieved such poor adoption and use
would motivate some worrying about having made some poor decisions. A
quick response that says "we talked about that" but says no more seems a
little bit facile.
Yet your response continues down the path of "What was decided was fine. So
let's dismiss expressions of concerns about it by citing a previous decision,
as if that choice was inevitable." In particular, my point was that a
v6-specific API was not immediately required.
The approach to IPv6 could have been vastly more incremental, so as to make
its adoption vastly less disruptive. But you have to start by considering the
benefits of such an approach.
Brian, the approach to IPv6 ignored protecting the installed base and ignored
finding a way to have the lowest possible barriers to adoption. As 15 years
of non-adoption has demonstrated, the value proposition for adopters also was
not compelling.
To repeat: At some point, it would help to take history as being instructive,
rather than to dismiss attempts at considering alternatives.
This might not change the situation with IPv6, but it could have an effect on
other, future work.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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